Left ventricular hypertrophy (LVH) in hypertensive subjects is associated with an increased prevalence of ventricular arrhythmias. To evaluate the effect of antihypertensive treatment on cardiac arrhythmias (CA) and transient episodes of myocardial ischemia (TEMI), we studied 46 hypertensive patients with LVH, divided into four groups randomly treated with enalapril, hydrochlorothiazide (HCTZ), atenolol, or verapamil (SR-V) for 6 months. Office blood pressure and office heart rate values were recorded, in basal conditions, after 1 and 6 months of treatment, and all patients underwent echocardiography, electrocardiographic Holter monitoring, and stress testing. All drugs significantly lowered blood pressure, whereas left ventricular mass index was reduced by atenolol, enalapril, and SR-V, but not by HCTZ. Treatment induced a significant reduction in the number of patients with supraventricular arrhythmias (35 v 15, P < .034, and 28 v 8, excluding patients treated with HCTZ, P < .008). The number of patients with ventricular arrhythmias was also reduced (32 v 16 considering all groups, P < .08, and 24 v 9, excluding patients treated with HCTZ, P < .04). The number of TEMI during Holter monitoring significantly decreased from 47 to 23 (P = .043) in all patients, and from 39 to 14 (P = .013) excluding patients treated with HCTZ. In all groups, irrespective of treatment, a reduction of blood pressure, heart rate, and systolic blood pressure/heart rate product measured by exercise stress test was observed. The present study shows that in hypertensive patients with LVH, antihypertensive treatment with atenolol, enalapril and SR-V reduces LVH and decreases the prevalence of CA and TEMI. Treatment with HCTZ during the 6-month study did not alter LVH and did not appear to reduce CA and TEMI.